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Yao Q, Mascarenhas dos Santos AC, Zhang H, Mañas A, Hussaini A, Kim U, Xu C, Basheer S, Tasaki S, Xiang J. Unconventional Source of Neurotoxic Protein Aggregation from Organelle Off-Target Bax∆2 in Alzheimer's Disease. Biomolecules 2023; 13:970. [PMID: 37371550 PMCID: PMC10296721 DOI: 10.3390/biom13060970] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 05/30/2023] [Accepted: 06/06/2023] [Indexed: 06/29/2023] Open
Abstract
Protein aggregates are a hallmark of Alzheimer's disease (AD). Extensive studies have focused on β-amyloid plaques and Tau tangles. Here, we illustrate a novel source of protein aggregates in AD neurons from organelle off-target proteins. Bax is a mitochondrial pore-forming pro-death protein. What happens to Bax if it fails to target mitochondria? We previously showed that a mitochondrial target-deficient alternatively spliced variant, Bax∆2, formed large cytosolic protein aggregates and triggered caspase 8-mediated cell death. Bax∆2 protein levels were low in most normal organs and the proteins were quickly degraded in cancer. Here, we found that 85% of AD patients had Bax∆2 required alternative splicing. Increased Bax∆2 proteins were mostly accumulated in neurons of AD-susceptible brain regions. Intracellularly, Bax∆2 aggregates distributed independently of Tau tangles. Interestingly, Bax∆2 aggregates triggered the formation of stress granules (SGs), a large protein-RNA complex involved in AD pathogenesis. Although the functional domains required for aggregation and cell death are the same as in cancer cells, Bax∆2 relied on SGs, not caspase 8, for neuronal cell death. These results imply that the aggregation of organelle off-target proteins, such as Bax∆2, broadens the scope of traditional AD pathogenic proteins that contribute to the neuronal stress responses and AD pathogenesis.
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Affiliation(s)
- Qi Yao
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA (C.X.)
| | | | - Huaiyuan Zhang
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA (C.X.)
| | - Adriana Mañas
- Department of Laboratory Medicine, Lund University, 22381 Lund, Sweden
| | - Ammarah Hussaini
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA (C.X.)
| | - Ujin Kim
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA (C.X.)
| | - Congtai Xu
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA (C.X.)
| | - Sana Basheer
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA (C.X.)
| | - Shinya Tasaki
- Rush Alzheimer’s Disease Center, Rush University Medical Center, Chicago, IL 60612, USA
| | - Jialing Xiang
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA (C.X.)
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2
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Yao Q, Zhang H, Standish C, Grube J, Mañas A, Xiang J. Expression profile of the proapoptotic protein Bax in the human brain. Histochem Cell Biol 2023; 159:209-220. [PMID: 35951115 DOI: 10.1007/s00418-022-02146-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/27/2022] [Indexed: 11/27/2022]
Abstract
Bax is a well-known universal proapoptotic protein. Bax protein is detected in almost all human organs, and its expression levels can be correlated with disease progression and therapeutic efficacy in certain settings. Interestingly, increasing evidence has shown that mature neuronal cell death is often not typical apoptosis. Most results on the expression of Bax proteins (predominantly Baxα) in the human brain come from disease-oriented studies, and the data on Bax protein expression in the normal brain are limited and lack consistency due to many variable factors. Here, we analyzed Bax RNA and protein expression data from multiple databases and performed immunostaining of over 80 samples from 25 healthy subjects across 7 different brain regions. We found that Bax protein expression was heterogeneous across brain regions and individual subjects. Both neurons and glial cells, such as astrocytes, could be Bax positive, but Bax positivity appeared to be highly selective, even within the same cell type in the same region. Furthermore, Bax proteins could be localized in the cytosol (evenly spread or concentrated to one region), nucleus or nucleolus depending on the cell type. Such variation and distribution in Bax expression suggest that Bax may function differently in the human brain than in other organs.
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Affiliation(s)
- Qi Yao
- Department of Biology, Lewis College of Science and Letters, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL, 60616, USA
| | - Huaiyuan Zhang
- Department of Biology, Lewis College of Science and Letters, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL, 60616, USA
| | - Collin Standish
- Department of Biology, Lewis College of Science and Letters, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL, 60616, USA
| | - Joshua Grube
- Department of Biology, Lewis College of Science and Letters, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL, 60616, USA
| | - Adriana Mañas
- Department of Biology, Lewis College of Science and Letters, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL, 60616, USA
| | - Jialing Xiang
- Department of Biology, Lewis College of Science and Letters, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL, 60616, USA.
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3
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A Structural Model for Bax∆2-Mediated Activation of Caspase 8-Dependent Apoptosis. Int J Mol Sci 2020; 21:ijms21155476. [PMID: 32751845 PMCID: PMC7432750 DOI: 10.3390/ijms21155476] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 07/26/2020] [Accepted: 07/29/2020] [Indexed: 01/28/2023] Open
Abstract
Bax∆2 is a pro-apoptotic anti-tumor protein in the Bax family. While most of the Bax family causes cell death by targeting mitochondria, Bax∆2 forms cytosolic aggregates and activates caspase 8-dependent cell death. We previously showed that the Bax∆2 helix α9 is critical for caspase 8 recruitment. However, the interaction between these two proteins at the structural level is unknown. In this in silico study, we performed molecular dynamics (MD) simulations and protein-protein docking on Bax∆2 variants. The results suggest that the Bax∆2 variants have different stable states. Mutating the Baxα mitochondria-targeting signal [L26P/L27P] appears to introduce a kink into helix α1. Protein-protein docking suggests that helices α9 of both wild-type Bax∆2 and Bax∆2 caspase 8 binding-deficient mutant [L164P] can fit in the same caspase 8 binding site, but the mutant is unable to fit as well as wild-type Bax∆2. Together, these data point to a structural basis for explaining Bax∆2 function in caspase 8-dependent cell death.
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Immunohistochemical detection of the pro-apoptotic Bax∆2 protein in human tissues. Histochem Cell Biol 2020; 154:41-53. [PMID: 32200452 DOI: 10.1007/s00418-020-01874-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/13/2020] [Indexed: 12/11/2022]
Abstract
The pro-apoptotic Bax isoform Bax∆2 was originally discovered in cancer patients with a microsatellite guanine deletion (G8 to G7). This deletion leads to an early stop codon; however, when combined with the alternative splicing of exon 2, the reading frame is restored allowing production of a full-length protein (Bax∆2). Unlike the parental Baxα, Bax∆2 triggers apoptosis through a non-mitochondrial pathway and the expression in human tissues was unknown. Here, we analyzed over 1000 tissue microarray samples from 13 different organs using immunohistochemistry. Bax∆2-positive cells were detected in all examined organs at low rates (1-5%) and mainly scattered throughout the connective tissues. Surprisingly, over 70% of normal colon samples scored high for BaxΔ2-positive staining. Only 7% of malignant colon samples scored high, with most high-grade tumors being negative. A similar pattern was observed in most organs examined. We also showed that both Baxα and Bax∆2 can co-exist in the same cells. Genotyping showed that the majority of Bax∆2-positive normal tissues contain no G7 mutation, but an unexpected high rate of G9 was observed. Although the underlying mechanism remains to be explored, the inverse correlation of Bax∆2 expression with tissue malignancy suggests that it may have a clinical implication in cancer development and treatment.
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5
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Chen X, Wang L, Roozbahani GM, Zhang Y, Xiang J, Guan X. Nanopore label-free detection of single-nucleotide deletion in Baxα/BaxΔ2. Electrophoresis 2018; 39:2410-2416. [PMID: 29998460 PMCID: PMC6168411 DOI: 10.1002/elps.201800193] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Revised: 06/14/2018] [Accepted: 07/01/2018] [Indexed: 12/13/2022]
Abstract
Baxα, a key tumor suppressor gene, will not be expressed correctly as a result of single nucleotide mutation in its microsatellite region; Instead, BaxΔ2, an isoform of Baxα, is often produced. In addition, lack of the exon 2 due to an alternative splicing, BaxΔ2 has the same sequence as Baxα except single base deletion from eight continuous guanines (G8) to G7. Most of the currently available methods for Bax∆2 detection are inefficient and time-consuming, and/or require the use of labels or dyes. In this work, we reported a label-free nanopore sensing strategy to differentiate between Baxα and BaxΔ2 with a DNA polymer as a molecular probe based on alternative spliced sequences. Two DNA molecules were designed to selectively detect Baxα and BaxΔ2, respectively. The method was rapid, accurate, and highly sensitive: picomolar concentrations of target nucleic acids could be detected in minutes. Our developed simple and fast nanopore-based detection strategy is not only useful for distinguishing between Baxα and Bax∆2, but also provides a useful tool for detection of other single-base mutations in genetic diagnosis.
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Affiliation(s)
- Xiaohan Chen
- Department of Chemistry, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Liang Wang
- Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, PR China
| | - Golbarg M Roozbahani
- Department of Chemistry, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Youwen Zhang
- Department of Chemistry, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Jialing Xiang
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Xiyun Guan
- Department of Chemistry, Illinois Institute of Technology, Chicago, IL 60616, USA
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Mañas A, Davis A, Lamerand S, Xiang J. Detection of pro-apoptotic Bax∆2 proteins in the human cerebellum. Histochem Cell Biol 2018; 150:77-82. [PMID: 29663074 DOI: 10.1007/s00418-018-1669-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/10/2018] [Indexed: 12/17/2022]
Abstract
Bax∆2 is a pro-apoptotic protein originally discovered in colon cancer patients with high microsatellite instability. Unlike most pro-apoptotic Bax family members, Bax∆2 mediates cell death through a non-mitochondrial caspase 8-dependent pathway. In the scope of analyzing the distribution of Bax∆2 expression in human tissues, we examined a panel of human brain samples. Here, we report four cerebellar cases in which the subjects had no neurological disorder or disease documented. We found Bax∆2 positive cells scattered in all areas of the cerebellum, but most strikingly concentrated in Purkinje cell bodies and dendrites. Two out the four subjects tested had strong Bax∆2-positive staining in nearly all Purkinje cells; one was mainly negative; and one had various levels of positive staining within the same sample. Further genetic analysis of the Purkinje cell layer, collected by microdissection from two subjects, showed that the samples contained G7 and G9 Bax microsatellite mutations. Both subjects were young and had no diseases reported at the time of death. As the distribution of Bax∆2 is consistent with that known for Baxα, but in a less ubiquitous manner, these results may imply a potential function of Bax∆2 in Purkinje cells.
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Affiliation(s)
- Adriana Mañas
- Department of Biology, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL, 60616, USA
| | - Aislinn Davis
- Department of Biology, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL, 60616, USA
| | - Sydney Lamerand
- Department of Biology, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL, 60616, USA
| | - Jialing Xiang
- Department of Biology, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL, 60616, USA.
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7
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Mañas A, Chen W, Nelson A, Yao Q, Xiang J. BaxΔ2 sensitizes colorectal cancer cells to proteasome inhibitor-induced cell death. Biochem Biophys Res Commun 2018; 496:18-24. [PMID: 29291406 PMCID: PMC6022363 DOI: 10.1016/j.bbrc.2017.12.156] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Accepted: 12/26/2017] [Indexed: 12/23/2022]
Abstract
Proteasome inhibitors, such as bortezomib and carfilzomib, are FDA approved for the treatment of hemopoietic cancers, but recent studies have shown their great potential for treatment of solid tumors. BaxΔ2, a unique proapoptotic Bax isoform, promotes non-mitochondrial cell death and sensitizes cancer cells to chemotherapy. However, endogenous BaxΔ2 proteins are unstable and susceptible to proteasomal degradation. Here, we screened a panel of proteasome inhibitors in colorectal cancer cells with different Bax statuses. We found that all proteasome inhibitors tested were able to block BaxΔ2 degradation without affecting the level of Baxα or Bcl-2 proteins. Among the inhibitors tested, only bortezomib and carfilzomib were able to induce differential cell death corresponding to the distinct Bax statuses. BaxΔ2-positive cells had a significantly higher level of cell death at low nanomolar concentrations than Baxα-positive or Bax-negative cells. Furthermore, bortezomib-induced cell death in BaxΔ2-positive cells was predominantly dependent on the caspase 8/3 pathway, consistent with our previous studies. These results imply that BaxΔ2 can selectively sensitize cancer cells to proteasome inhibitors, enhancing their potential to treat colon cancer and other solid tumors.
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Affiliation(s)
- Adriana Mañas
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Wenjing Chen
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Adam Nelson
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Qi Yao
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Jialing Xiang
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA.
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8
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Mañas A, Wang S, Nelson A, Li J, Zhao Y, Zhang H, Davis A, Xie B, Maltsev N, Xiang J. The functional domains for Bax∆2 aggregate-mediated caspase 8-dependent cell death. Exp Cell Res 2017; 359:342-355. [PMID: 28807790 PMCID: PMC5718386 DOI: 10.1016/j.yexcr.2017.08.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 08/07/2017] [Accepted: 08/08/2017] [Indexed: 01/09/2023]
Abstract
Bax∆2 is a functional pro-apoptotic Bax isoform having alterations in its N-terminus, but sharing the rest of its sequence with Baxα. Bax∆2 is unable to target mitochondria due to the loss of helix α1. Instead, it forms cytosolic aggregates and activates caspase 8. However, the functional domain(s) responsible for BaxΔ2 behavior have remained elusive. Here we show that disruption of helix α1 makes Baxα mimic the behavior of Bax∆2. However, the other alterations in the Bax∆2 N-terminus have no significant impact on aggregation or cell death. We found that the hallmark BH3 domain is necessary but not sufficient for aggregation-mediated cell death. We also noted that the core region shared by Baxα and Bax∆2 is required for the formation of large aggregates, which is essential for BaxΔ2 cytotoxicity. However, aggregation by itself is unable to trigger cell death without the C-terminus. Interestingly, the C-terminal helical conformation, not its primary sequence, appears to be critical for caspase 8 recruitment and activation. As Bax∆2 shares core and C-terminal sequences with most Bax isoforms, our results not only reveal a structural basis for Bax∆2-induced cell death, but also imply an intrinsic potential for aggregate-mediated caspase 8-dependent cell death in other Bax family members.
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Affiliation(s)
- Adriana Mañas
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Sheng Wang
- Human Genetics Department, Computation Institute, University of Chicago, Chicago, IL 60637, USA
| | - Adam Nelson
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Jiajun Li
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Yu Zhao
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Huaiyuan Zhang
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Aislinn Davis
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Bingqing Xie
- Department of Computer Science, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Natalia Maltsev
- Human Genetics Department, Computation Institute, University of Chicago, Chicago, IL 60637, USA
| | - Jialing Xiang
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA.
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Radhakrishnan H, Ilm K, Walther W, Shirasawa S, Sasazuki T, Daniel PT, Gillissen B, Stein U. MACC1 regulates Fas mediated apoptosis through STAT1/3 - Mcl-1 signaling in solid cancers. Cancer Lett 2017. [PMID: 28649004 DOI: 10.1016/j.canlet.2017.06.020] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
MACC1 was identified as a novel player in cancer progression and metastasis, but its role in death receptor-mediated apoptosis is still unexplored. We show that MACC1 knockdown sensitizes cancer cells to death receptor-mediated apoptosis. For the first time, we provide evidence for STAT signaling as a MACC1 target. MACC1 knockdown drastically reduced STAT1/3 activating phosphorylation, thereby regulating the expression of its apoptosis targets Mcl-1 and Fas. STAT signaling inhibition by the JAK1/2 inhibitor ruxolitinib mimicked MACC1 knockdown-mediated molecular signatures and apoptosis sensitization to Fas activation. Despite the increased Fas expression, the reduced Mcl-1 expression was instrumental in apoptosis sensitization. This reduced Mcl-1-mediated apoptosis sensitization was Bax and Bak dependent. MACC1 knockdown also increased TRAIL-induced apoptosis. MACC1 overexpression enhanced STAT1/3 phosphorylation and increased Mcl-1 expression, which was abrogated by ruxolitinib. The central role of Mcl-1 was strengthened by the resistance of Mcl-1 overexpressing cells to apoptosis induction. The clinical relevance of Mcl-1 regulation by MACC1 was supported by their positive expression correlation in patient-derived tumors. Altogether, we reveal a novel death receptor-mediated apoptosis regulatory mechanism by MACC1 in solid cancers through modulation of the STAT1/3-Mcl-1 axis.
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Affiliation(s)
- Harikrishnan Radhakrishnan
- Translational Oncology of Solid Tumors, Experimental and Clinical Research Center, Charité - Universitätsmedizin Berlin, Max-Delbrück-Center for Molecular Medicine, Berlin, Germany; Berlin School of Integrative Oncology, Charité - Universitätsmedizin Berlin, Germany
| | - Katharina Ilm
- Translational Oncology of Solid Tumors, Experimental and Clinical Research Center, Charité - Universitätsmedizin Berlin, Max-Delbrück-Center for Molecular Medicine, Berlin, Germany
| | - Wolfgang Walther
- Translational Oncology of Solid Tumors, Experimental and Clinical Research Center, Charité - Universitätsmedizin Berlin, Max-Delbrück-Center for Molecular Medicine, Berlin, Germany
| | - Senji Shirasawa
- Department of Cell Biology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
| | | | - Peter T Daniel
- Clinical and Molecular Oncology, Experimental and Clinical Research Center, Charité - Universitätsmedizin Berlin, Max-Delbrück-Center for Molecular Medicine, Berlin, Germany
| | - Bernhard Gillissen
- Clinical and Molecular Oncology, Experimental and Clinical Research Center, Charité - Universitätsmedizin Berlin, Max-Delbrück-Center for Molecular Medicine, Berlin, Germany
| | - Ulrike Stein
- Translational Oncology of Solid Tumors, Experimental and Clinical Research Center, Charité - Universitätsmedizin Berlin, Max-Delbrück-Center for Molecular Medicine, Berlin, Germany; German Cancer Consortium (DKTK), Heidelberg, Germany.
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10
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Yamamoto H, Imai K. Microsatellite instability: an update. Arch Toxicol 2015; 89:899-921. [PMID: 25701956 DOI: 10.1007/s00204-015-1474-0] [Citation(s) in RCA: 150] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Accepted: 02/09/2015] [Indexed: 02/08/2023]
Abstract
Deficient DNA mismatch repair (MMR) results in a strong mutator phenotype known as microsatellite instability (MSI), which is a hallmark of Lynch syndrome-associated cancers. MSI is characterized by length alterations within simple repeated sequences that are called microsatellites. Lynch syndrome is primarily caused by mutations in the MMR genes, mainly MLH1 and MSH2, and less frequently in MSH6, and rarely PMS2, and large genomic rearrangements account for 5-20 % of all mutations. Germ line hemiallelic methylations of MLH1 or MSH2 are termed as epimutations and have been identified as causative of Lynch syndrome. Moreover, germ line 3' deletions of EPCAM gene is involved in MSH2 methylation. MSI is also observed in about 15 % of sporadic colorectal cancer (CRC), gastric cancer (GC), and endometrial cancer (EC), and at lower frequencies in other cancers, often in association with hypermethylation of the MLH1 gene. Trimethylation of histone H3 on Lys36 (H3K36 me3) is an epigenetic histone mark that was required for DNA MMR in vivo. Thus, mutations in the H3K36 trimethyltransferase SETD2 have been reported as a potential cause of MSI. Genetic, epigenetic, and transcriptomic differences have been identified between cancers with and without MSI. Recent comprehensive molecular characterizations of CRC, EC, and GC by The Cancer Genome Atlas indicate that MSI+ cancers are distinct biological entities. The BRAF V600E mutation is specifically associated with sporadic MSI+ CRCs with methylated MLH1, but is not associated with Lynch syndrome-related CRCs. Accumulating evidence indicates a role of interactions between MSI and microRNA (miRNA) in the pathogenesis of MSI-positive (MSI+) cancer. As another new mechanism underlying MSI, overexpression of miR-155 or miR-21 has been shown to downregulate the expression of the MMR genes. Gene targets of frameshift mutations caused by MSI are involved in various cellular functions, including DNA repair (MSH3 and MSH6), cell signaling (TGFBR2 and ACVR2A), apoptosis (BAX), epigenetic regulation (HDAC2 and ARID1A), and miRNA processing (TARBP2 and XPO5), and a subset of MSI+ CRCs reportedly shows the mutated miRNA machinery phenotype. Moreover, microsatellite repeats in miRNA genes, such as hsa-miR-1273c, may be novel MSI targets for CRC, and mutations in noncoding regulatory regions of MRE11, BAX (BaxΔ2), and HSP110 (HSP110ΔE9) may affect the efficiency of chemotherapy. Thus, analyses of MSI and its related molecular alterations in cancers are increasingly relevant in clinical settings, and MSI is a useful screening marker for identifying patients with Lynch syndrome and a prognostic factor for chemotherapeutic interventions. In this review, we summarize recent advances in the pathogenesis of MSI and focus on genome-wide analyses that indicate the potential use of MSI and related alterations as biomarkers and novel therapeutic targets.
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Affiliation(s)
- Hiroyuki Yamamoto
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, St. Marianna University School of Medicine, Kawasaki, 216-8511, Japan,
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Zhang H, Lin Y, Mañas A, Zhao Y, Denning MF, Ma L, Xiang J. BaxΔ2 Promotes Apoptosis through Caspase-8 Activation in Microsatellite-Unstable Colon Cancer. Mol Cancer Res 2014; 12:1225-32. [DOI: 10.1158/1541-7786.mcr-14-0162] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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